1. Field of the Invention
The present invention relates to microbial mannanases, more specifically to microbial enzymes exhibiting mannanase activity as their major enzymatic activity in the neutral and alkaline pH ranges; to a method of producing such enzymes; and to methods for using such enzymes in the paper and pulp, textile, oil drilling, cleaning, laundering, detergent, and cellulose fiber processing industries.
2. Description of Related Art
Mannan containing polysaccharides are a major component of the hemicellulose fraction in woods and endosperm in many leguminous seeds and in some mature seeds of non-leguminous plants. Essentially unsubstituted linear beta-1,4-mannan is found in some non-leguminous plants. Unsubstituted beta-1,4-mannan which is present e.g. in ivory nuts resembles cellulose in the conformation of the individual polysaccharide chains, and is water-insoluable. In leguminous seeds, water-soluble galactomannan is the main storage carbohydrate comprising up to 20% of the total dry weight. Galactomannans have a linear beta-1,4-mannan backbone substituted with single alpha-1,6-galactose, optionally substituted with acetyl groups. Mannans are also found in several monocotyledonous plants and are the most abundant polysaccharides in the cell wall material in palm kernel meal. Glucomannans are linear polysaccharides with a backbone of beta-1,4-linked mannose and glucose alternating in a more or less regular manner, the backbone optionally being substituted with galactose and/or acetyl groups. Mannans, galactomannans, glucomannans and galactoglucomannans (i.e. glucomannan backbones with branched galactose) contribute to more than 50% of the softwood hemicellulose. Moreover, the cellulose of many red algae contains a significant amount of mannose.
Mannanases have been identified in several Bacillus organisms. For example, Talbot et al. (Appl. Environ. Microbiol., 1990, 56(11): 3505–3510) describe a beta-mannanase derived from Bacillus stearothermophilus in dimer form having a molecular weight of 162 kDa and a pH optimum of 5.5–7.5. Mendoza et al. (World J. Microbiol. Biotech., 1994, 10(5):: 551–555) describe a beta-mannanase derived from Bacillus subtilis having a molecular weight of 38 kDa, an optimum activity at pH 5.0 and 55° C. and a pl of 4.8. JP-A-03047076 discloses a beta-mannanase derived from Bacillus sp., having a molecular weight of 37±3 kDa measured by gel filtration, a pH optimum of 8–10 and a pl of 5.3–5.4. JP-A-63056289 describes the production of an alkaline, thermostable beta-mannanase which hydrolyzes beta-1,4-D-mannopyranoside bonds of e.g. mannans and produces manno-oligosaccharides. JP-A-63036775 relates to the Bacillus microorganism FERM P-8856 which produces beta-mannanase and beta-mannosidase at an alkaline pH. JP-A-08051975 discloses alkaline beta-mannanases from alkalophilic Bacillus sp. AM-001 having molecular weights of 43±3 kDa and 57±3 kDa and a pH optimum of 8–10. A purified mannanase from Bacillus amyloliquefaciens useful in the bleaching of pulp and paper and a method of preparation thereof is disclosed in WO 97/11164. WO 91/18974 describes a hemicellulase such as a glucanase, xylanase or mannanase active at an extreme pH and temperature. WO 94/25576 discloses an enzyme from Aspergillus aculeatus, CBS 101.43, exhibiting mannanase activity which may be useful for degradation or modification of plant or algae cell wall material. WO 93/24622 discloses a mannanase isolated from Trichoderma reseei useful for bleaching lignocellulosic pulps.
WO 95/35362 discloses cleaning compositions containing plant cell wall degrading enzymes having pectinase and/or hemicellulase and optionally cellulase activity for the removal of stains of vegetable origin and further discloses an alkaline mannanase from the strain C11SB.G17.
It is an object of the present invention to provide a novel and efficient enzyme exhibiting mannanase activity also in the alkaline pH range, e.g. when applied in cleaning compositions or different industrial processes.